You probably don't want to hear this, but here goes anyway.
The human skin serves many functions and one of the primary ones is to keep out alien life forms and toxins. Break the skin, particularly in a non-sterile environment, and you risk the introduction of viruses, bacteria, protozoans and metazoans that can cause infection as well as toxins that can trigger an allergic response. The bite of an octopus can qualify as a risk in this respect. I've been bitten by O. cyanea (lots of blood, not much venom) and O. rubescens (blood and a response similar to a bad bee sting) and I can't imagine why anyone would want promote such behavior. I guess it must be sort of like putting your tongue on the pump handle in the middle of winter.
Let me give you a non-octopod example of what can go wrong. A few years ago a surgeon in South Africal wrote me asking if I knew anything about stomatopod-carried infectious agents. He had been stabbed by one, developed a bacterial infections that was eating away the connective tissue of his hand and eventually resorted to amputation. The bacterium could not be identified and did not respond to any of the usual broad spectrum antibiotics. It is not clear if the bacterium was associated with the stomatopod - it could have simply been in the environment and was introduced when the skin was broken, but either way, the consequences were very serious. Even if you aren't worried about what might be living in an octopus's mouth or developing an allergic response to its saliva, there are several organisms associated with marine aquaria that can cause serious infections. It really isn't worth the risk.